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| United States Patent |
5,162,382
|
|
Carswell
, et al.
|
*
November 10, 1992
|
Polyurethanes containing multipurpose additives
Abstract
A flexible or semi-flexible polyurethane foam composition prepared from a
formulation comprising a catalytic amount of an additive containing (1) a
urea compound, and (2) a transition metal salt of a carboxylic acid
wherein the metal is selected from Groups I-B, II-B, V-A, IV-B, V-B, VI-B,
VII-B or VIII of the Periodic Table of the Elements; the additive
containing a sufficient quantity of at least one amine group-containing
material such that the transition metal salt is soluble in the additive;
and water as a blowing agent. In preferred embodiments water is the sole
blowing agent. The polyurethanes exhibit relatively short demolding times
and improved mold release properties. They also show a reduced tendency to
cause discoloration or staining of vinyl-based polymeric calddings such as
polyvinyl chloride.
| Inventors:
|
Carswell; Robert (Lake Jackson, TX);
Bernardi; Hugo E. (Lake Jackson, TX)
|
| Assignee:
|
The Dow Chemical Company (Midland, MI)
|
| [*] Notice: |
The portion of the term of this patent subsequent to December 3, 2008
has been disclaimed. |
| Appl. No.:
|
734373 |
| Filed:
|
July 22, 1991 |
| Current U.S. Class: |
521/51; 428/424.6; 521/105; 521/137; 521/155; 521/163; 528/73 |
| Intern'l Class: |
C08G 018/16; C08G 018/04; C08G 018/18 |
| Field of Search: |
521/105,51,137,163,155
528/73
|
References Cited
U.S. Patent Documents
| 4125487 | Nov., 1978 | Olstowski | 521/137.
|
Primary Examiner: Kight, III; John
Assistant Examiner: Wright; Shelley
Parent Case Text
CROSS-REFERENCE TO A RELATED APPLICATION
The present application is a continuation-in-part application of U. S.
application Ser. No. 398,802, filed Aug. 25, 1989, currently allowed.
Claims
What is claimed is:
1. A polyurethane flexible or semi-flexible foam composition prepared from
a formulation comprising
(A) a catalytic amount of an additive containing (1) a urea compound and
(2) a transition metal salt of a carboxylic acid wherein the metal is
selected from Groups 1-B, II-B, V-A, IV-B, V-B, VI-B, VII-B or VIII of the
Periodic Table of the Elements: the additive containing a sufficient
quantity of at least one amine group-containing material such that the
transition metal salt is soluble in the additive; and
(B) water as a blowing agent.
2. The composition of claim 1 wherein water is the sole blowing agent.
3. The composition of claim 1 further comprising at least one amine
terminated polyether polyol.
4. The composition of claim 3 wherein the amine group-containing material
is an unsubstituted or ether-substituted aliphatic or cycloaliphatic
primary or secondary mono-amine compound; a trialkyl amine; a hydroxyl
amine; a tertiary amine; an amine terminated polyether having a molecular
weight less than about 500, hexamethylene diamine, diethylenetriamine; a
hydrocarbyl substituted aromatic amine; or a mixture thereof.
5. The composition of claim 1 wherein the transition metal carboxylate salt
has a metal cation selected from Ti, Zr, Ta, Cr, Mn, Mo, Fe, Co, Ni, Cu,
Sb, Bi, and Zn.
6. The composition of claim 5 wherein the transition metal carboxylate salt
has a metal cation selected from Zn, Cu, Sb, and Cd.
7. The composition of claim 6 wherein the transition metal carboxylate salt
has a Zn cation.
8. The composition of claim 9 wherein the transition metal carboxylate salt
has a carboxylate anion having from 8 to 21 carbon atoms.
9. The composition of claim 8 wherein the urea compound is represented by
Formula I:
##STR2##
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are inert substituents.
10. The composition of claim 9 wherein in Formula I each of R.sup.1,
R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group
consisting of hydrogen, alkyl groups, aryl groups, arylalkyl groups,
cycloalkyl groups, which groups are unsubstituted or inertly substituted.
11. The composition of claim 10 wherein in Formula I, at least two of
R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are hydrogen.
12. The composition of claim 11 wherein in Formula I, at least two of the
hydrogen atoms are on the same nitrogen atom.
13. The composition of claim 12 wherein in Formula I, at least three of
R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are hydrogen atoms.
14. The composition of claim 13 wherein the urea compound is urea.
15. The composition of claim 1 wherein the polyurethane polymer is formed
in a reaction injection molding process.
16. The composition of claim 15 wherein the polymer has a demolding time of
less than about 60 seconds.
17. The composition of claim 1 wherein the polymer is an integral skin foam
and has a demolding time of less than about 4 minutes.
18. The composition of claim 17 wherein the polymer is an integral skin
foam and in the form of a shoe sole or shoe inner sole.
19. A cladded polyurethane composition prepared from a formulation
comprising a catalytic amount of an additive containing
(A) a urea compound, and
(B) a transition metal salt of a carboxylic acid wherein said metal is
selected from Groups I-B, II-B, V-A, IV-B, V-B, VI-B, VII-B or VIII of the
Periodic Table of the Elements; the additive containing a sufficient
quantity of at least one amine group-containing material such that the
transition metal salt is soluble in the additive,
wherein the polyurethane prepared therefrom is cladded on at least one
surface with a vinyl-based polymer.
20. The composition of claim 19 wherein the formulation further comprises
water as a blowing agent.
21. The composition of claim 20 wherein water is the sole blowing agent.
22. The composition of claim 19 wherein the vinyl-based polymer is
polyvinyl chloride.
Description
BACKGROUND OF THE INVENTION
This invention relates to additives useful in preparing polyurethane
formulations to impart specific properties to the final polyurethane
product.
As is well known in the polyurethane art, polyurethanes can be prepared in
a variety of forms. One commonly prepared form includes foamed
polyurethanes, in which the density of the product is reduced by
introduction of a blowing agent. Foamed polyurethanes are frequently
molded into a desired final shape, and may be categorized as flexible,
i.e., relatively low density, foams or as semi-flexible, i.e., relatively
higher density materials. Polyurethanes may also be prepared as
elastomeric compositions. in which there is little or no density reduction
and also often significant stiffness, as is the case with reaction
injection molded (RIM) materials.
In the case of molded materials, a frequently encountered problem is that
of release of the cured polyurethane article from the mold. Various
approaches have been tried to solve this problem with varying success.
Some notable examples include the use of a metal carboxylate salt, such as
zinc stearate, as is disclosed in, for example, U.S. Pat. Nos. 4,876.019
and 4,585,803. This additive is particularly successful in increasing the
number of releases of a RIM article from the mold without undesirable
sacrifice of the final physical properties of the article.
Another problem encountered in preparing molded polyurethane materials is
that, for a number of applications particularly including automotive
interior applications, the molding of the polyurethane is done directly on
a sheet, or "cladding," of a vinyl-based polymer such as polyvinyl
chloride. Over time there is a well-known tendency for the vinyl-based
polymeric cladding to discolor or "stain", thereby reducing the
marketability of the final product. Exposure to climatic extremes, such as
is encountered by polyvinyl chloride-clad polyurethanes in vehicle
dashboards, increases the rate of this staining.
Finally, it is well known in the art that certain catalysts are needed for
many formulations in order to ensure adequate polyurethane cure to allow
relatively rapid demolding time. For many purposes, especially in the
automotive industry, such demolding is preferably accomplished in less
than about 60 seconds from injection of the reactants into the mold. To
speed the reaction and thereby allow processing by automated RIM
equipment, tin carboxylate catalysts are frequently used, such as, for
example, dimethyltin dilaurate.
Thus, it would be desirable to find an additive or group of additives for
use in polyurethane formulations that enhances mold release properties,
particularly as to multiple releases; that reduces the staining or
discoloration of vinyl-based polymeric cladding adhered thereto; and that
shows sufficient catalytic activity to allow for acceptable demolding
times for use particularly in automated processes of various kinds.
SUMMARY OF THE INVENTION
In one aspect, the invention is a polyurethane formulation comprising (A) a
catalytic amount of an additive containing (1) a urea compound, and (2) a
transition metal salt of a carboxylic acid wherein the metal is selected
from Groups 1-B, II-B, V-A, IV-B, V-B, VI-B, VII-B or VIII of the Periodic
Table of the Elements, the additive containing a sufficient quantity of at
least one amine group-containing material such that the transition metal
salt is soluble in the additive; and (B) water as a blowing agent. In
preferred embodiments the polyurethane is a polyurethane foam, flexible or
semi-flexible, and water is the sole blowing agent.
In another aspect, the invention is a polyurethane foam, which may be
flexible or semi-flexible, prepared from the formulation described
hereinabove, having adhered thereto a vinyl-based polymeric cladding.
In other aspects, the invention includes processes of preparing the
polyurethanes.
Compositions of the present invention exhibit the desirable properties of
sufficiently rapid cure to allow acceptable demolding times for automated
processing: enhanced mold release, particularly for semi-flexible
polyurethane materials, and more particularly for water blown
semi-flexible materials: and reduced tendency to cause discoloration or
staining of vinyl-based polymeric cladding.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The formulations of the present invention include, first of all, at least
one urea compound, which is suitably urea, either substituted or
unsubstituted. A substituted urea advantageously is an inertly substituted
urea, that is, it has substitution which does not interfere undesirably
with compatibilization of the composition or with catalysis of the
polyurethane-forming reaction. Urea compounds used in the practice of the
invention preferably are of Formula I:
##STR1##
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are inert substituents.
Preferably, each of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently
selected from the group consisting of hydrogen, alkyl groups, aryl groups,
arylalkyl groups, cycloalkyl groups, which groups are unsubstituted or
inertly substituted. The inert substituents on the groups include, for
instance, ether groups such as alkoxy groups, aryloxy groups and the like:
fluorine, hydrogen, chlorine and hydroxy groups. The alkyl groups
preferably have from about 1 to about 20, more preferably from about 1 to
about 5 carbon atoms and include, for instance methyl, ethyl, propyl,
hydroxymethyl, and methoxypropyl groups and the like. The aryl groups
preferably have from about 6 to about 18, more preferably from about 6 to
about 10 carbon atoms and include, for instance phenyl, p-fluorophenyl.
4-chlorophenyl, and 4-methoxyphenyl groups and the like. The alkyl aryl
groups preferably have from about 7 to about 30, more preferably from
about 7 to about 25 carbon atoms and include, for instance p-methyl
phenyl, m-ethylphenyl and the like. The arylalkyl groups preferably have
from about 7 to about 10 carbon atoms and include, for instance benzyl,
2-phenylmethyl groups and the like. The cycloalkyl groups preferably have
from about 4 to about 10 carbon atoms for instance cyclohexyl, methyl
cyclohexyl, and cyclobutyl groups and the like. The alkoxy groups
preferably have from about 1 to about 25 and include, for instance
methoxy, ethoxy, and propoxy groups and the like. The aryloxy groups
preferably have from about 6 to about 30, more preferably from about 6 to
about 25 carbon atoms and include, for instance, phenoxy, and
p-fluorophenoxy groups and the like. Substituents having the indicated
ranges of carbon atoms are preferred because they exhibit desirable levels
of solubility as well as catalytic and compatibilizing activity in
combination with the metal carboxylates as described hereinbelow.
In Formula I, at least two of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
preferably hydrogen: more preferably, at least two of the hydrogen atoms
are on the same carbon atom (e.g. R.sup.1 and R.sup.2 are both hydrogen).
Most preferably, at least three, and even more preferably all 4 of
R.sup.1, R.sup.2 R.sup.3, and R.sup.4 are hydrogen atoms. Preferred urea
compounds include,:for example, urea, 1-methylurea, and 1,1-diethyl urea.
The most preferred compound is urea.
Secondly, the formulations of the present invention contain at least one
transition metal salt of a carboxylic acid (hereinafter transition metal
carboxylate). The transition metal carboxylates are the salts of a metal
cation from Groups IVB, VB, VIIB, VIII, IB, IIB and VA of the Periodic
Table of the Elements with at least one carboxylate anion, that is the
anion of an organic material having at least one carboxylic acid group.
All valences of the transition metals in the transition metal carboxylates
are preferably filled with carboxylate anions; alternatively, the
transition metal carboxylates include transition metal salts having
metal-metal bonds, or, preferably, ionic bonds to anions other than
carboxylate anions, but not bonds directly to carbon as in alkylmetals.
The transition metals include such metals as Ti, Zr, Ta, Cr, Mn, Mo, Fe,
Co, Ni, Cu, Sb, Bi, Zn and the like. Preferred metals are Zn, Cu, Sb, and
Cd: more preferred, Sb, Cd and Zn; and Zn, most preferred. These
preferences are based on stability and reactivity under conditions present
in polyurethane forming processes. Suitable carboxylate anions include
anions of saturated or unsaturated carboxylic acids having from about 2 to
about 30, preferably from about 8 to about 21 carbon atoms, more
preferably from about 10 to about 18 carbon atoms because these chain
lengths are more effective in internal mold release. Suitable transition
metal carboxylates preferably include zinc stearate, zinc laurate, zinc
myristate, zinc palmitate, copper stearate, copper laurate, copper oleate,
copper palmitate, cadmium laurate, cadmium stearate, cadmium palmitate;
antimony laurate, antimony stearate, nickel stearate, nickel oleate,
nickel palmitate, nickel laurate and the like. Particularly suitable are
the zinc carboxylates which include, for example, zinc stearate, zinc
oleate, zinc palmitate, zinc laurate, zinc stearoyl sarcosinate, zinc
oleoyl sarcosinate, zinc palmitoyl sarcosinate, zinc lauroyl sarcosinate;
with zinc stearate, zinc laurate, and zinc myristate being more preferred:
and zinc laurate being most preferred.
Together, the urea compound and transition metal carboxylate are present in
amounts sufficient to catalyze reaction of an active hydrogen-containing
components with a polyisocyanate and, when an alkylene glycol is used in
the formulation, in amounts which are also sufficient to compatibilize the
relatively high equivalent weight active hydrogen compound and the
alkylene glycol in the composition. Such compatibilization is described
more fully in the parent case hereto, which is U.S. patent application
Ser. No. 398,802, filed Aug. 25, 1989, currently allowed. The term
"compatibilize" is used herein to denote that the composition is capable
of remaining in a single phase (i.e., neither cloudy nor separated) for at
least 10 days of storage at a temperature of at least about 20.degree. C.
However, benefits of the combination of urea and the metal carboxylate as
used in the present invention can be seen whether or not such
compatibilization is needed.
The presence of sufficient urea compound and transition metal carboxylate
to provide sufficient reactivity of the composition in polyurethane
formation is indicated by formation of a gel which generally rapidly forms
a hard polymer within at least about 40 seconds, preferably from about 0.5
to about 25 seconds, more preferably from about 10 to about 20 seconds
from mixing of active hydrogen and polyisocyanate components. Preferably
there is sufficient catalytic activity to provide sufficient reactivity to
permit removal of a molded part from the mold in less than about 60
seconds from the time components are injected into the mold, which is
defined as the demolding time. The demolding time is preferably from about
1 to about 30 seconds, more preferably from about 1 to about 20 seconds,
which are the demolding times commonly found useful in automated RIM
processes. In the case of integral skin and semi-flexible foams however,
longer demolding times, preferably less than about 4 minutes, are
particularly suitable. Integral skin foams generally have interior
densities of from about 75 to about 450, preferably from about 150 to
about 350 Kg/m.sup.3 (kilograms/cubic meter), whereas other RIM produced
polyurethanes generally have densities of from about 600 to about 1500,
preferably from about 900 to about 1200 Kg/m.sup.3. Semi-flexible foams
generally have overall densities of from about 50 to about 200 Kg/m.sup.3.
Preferably, the amounts of urea compound are sufficient to compatibilize
the glycol, when present, and relatively high equivalent weight active
hydrogen compound and preferably range from a urea:glycol ratio
(weight:weight) of about 1:1 to about 1:15, more preferably about 1:2 to
1:12, and most preferably about 1:3 to about 1:6. An excess of urea
compound often results in formation of a gel in the active hydrogen
composition, especially when urea (unsubstituted) rather than a
substituted urea is used.
Preferably, from about 0.1 to about 10, more preferably from about 0.5 to
about 5, and most preferably from about 1 to about 3 parts by weight
transition metal carboxylate per 100 parts by weight of the relatively
high equivalent weight active hydrogen compounds which are present are
employed. The ratio of the urea compound to the transition metal
carboxylate is preferably from about 1:4 to about 10:1. more preferably
from about 1:2 to about 5:1. These amounts of the transition metal
carboxylate and urea compound help to ensure maintenance of sufficient
reactivity and desirable mold release characteristics for the
formulations, particularly for semi-flexible and water blown formulations
but also for a wide range of other types of polyurethane formulations, and
also provide compatibilization when formulations containing an alkylene
glycol are employed.
In addition to the relatively high equivalent weight active hydrogen
compound and glycol chain extender, compositions of the invention
preferably contain at least one amine. When the relatively high equivalent
weight active hydrogen compound contains amine groups, and both
compatibilization of any glycol in the composition, if needed, and
solution of the transition metal carboxylate can be achieved without an
additional amine compound, the additional amine compound is not needed.
Otherwise, an amine is generally needed. Use of an amine compound is
especially preferred when there are more than about 10 parts by weight of
glycol per hundred parts by weight of any incompatible relatively high
equivalent weight compound (usually having a molecular weight greater than
1,000) and when a flexural modulus of at least about 5,000 psi is desired
in a polyurethane prepared from the composition. Under certain
circumstances the amine compound can additionally provide catalysis, chain
extension, aid in mold release or other functions. Examples of amines
useful as chain extenders or cross-linking agents, for instance, are
described in U.S. Pat. Nos. 4,269,945; 4,433,067 and 4,444,910, which are
incorporated herein by reference in their entireties. Use as an active
hydrogen component, for instance, is described in U.S. Pat. Nos. 4,719,247
and 4,742,091, which are incorporated herein by reference in their
entireties. Use in an internal mold release composition, for instance, is
described in U.S. Pat. Nos. 4,876,019 and 4,585,803, which are
incorporated herein by reference in their entireties.
Suitable amines which can be employed herein as a component in the
composition of the invention include any aliphatic, cycloaliphatic, or
aromatic compound containing at least one primary, secondary or tertiary
amine group. The amines are, optionally, inertly substituted, that is,
substituted with groups which do not undesirably interfere with the
reactions of the amine group. Inert substitution includes, for instance,
alkyl groups, cycloalkyl groups, aryl groups, arylalkyl groups, nitro
groups, sulfate groups, sulfone groups, ether groups, hydroxyl groups,
urethane groups, urea groups and the like. Amines having alkyl, aryl,
cycloalkyl, arylalkyl, ether and hydroxyl groups are preferred.
Preferred amines include unsubstituted or ether-substituted aliphatic or
cycloaliphatic primary or secondary mono-amine compounds: trialkyl amines;
hydroxyl amines, including alkyl diethanolamines, diethanolamine and
dialkyl hydroxyl amines; tertiary amines such as those described in U.S.
Pat. No. 4,585,803. and low equivalent weight aliphatic and aromatic amine
active hydrogen containing compounds, such as amine terminated polyethers
of less than about 500, preferably from about 200 to about 500 molecular
weight, hexamethylene diamine, diethylenetriamine, and hydrocarbyl
substituted aromatic amines such as, for example,
diethylenetoluenediamine. An unsubstituted or ether-substituted aliphatic
or cycloaliphatic primary mono-amine compound preferably contains from
about 4 to about 8 carbon atoms. An unsubstituted or ether-substituted
aliphatic or cycloaliphatic secondary monoamine compound preferably
contains from about 6 to about 12 carbon atoms. An alkyl diethanol amine
preferably has an alkyl group containing from about 2 to about 8 carbon
atoms. A dialkyl hydroxyl amine preferably contains about 4 to about 10
carbon atoms. In a trialkylamine, each alkyl group preferably has from
about 2 to about 4 carbon atoms. Amines having these ranges of carbon
atoms are preferred because these amines are effective compatibilizers.
Amines described as useful with internal mold release agents in U.S. Pat.
No. 4,876,019, incorporated herein by reference in its entirety, are
particularly preferred because they are effective in achieving solution of
the internal mold release agents.
Suitable amines include, for example, oleyl amine, coco amine, tall oil
amine, ethanolamine, diethyltriamine, ethylenediamine, propanolamine,
aniline, mixtures thereof and the like. Other exemplary amines include
n-butylamine, amylamine, n-hexylamine, n-octylamine, sec-butylamine,
1-amino-2-ethoxyethane, 1-amino-1-methyl hexane, cyclohexylamine,
di-n-propylamine, ethylpropylamine, di-n-butylamine, di-n-hexylamine,
di-sec-butylamine, ethyldiethanolamine, n-propyldiethanolamine,
n-butyldiethanolamine, n-hexyldiethanolamine, diethylhydroxylamine,
di-n-propylhydroxylamine, di-n-butylhydroxylamine, triethylamine,
tri(n-propyl)amine, tri(n-butyl)amine, ethyl di(n-propyl)amine,
diethanolamine and the like. Suitable tertiary amines include
triethylenediamine, N-methyl morpholine, N-ethyl morpholine,
diethylethanolamine, N-coco morpholine, amino ethyl piperazine,
1-methyl-4-dimethylaminoethyl piperazine, 3-methoxy-N-dimethylpropylamine,
N,N-diethyl-3-diethylaminopropylamine, dimethylbenzyl amine and the like.
Particularly suitable amines include aminated polyoxyalkylene glycols,
hexamethylene diamine, diethylene triamine, and hydrocarbyl substituted
aromatic amines such as diethylenetoluenediamine.
The amount of amine present is not critical to this invention, but is
advantageously determined by the purpose served by the amine in a given
formulation. Preferably such amine is sufficient to compatibilize the mold
release agent according to the teachings of U.S. Pat. Nos. 4,876,019 or
4,585,803. The invention is most useful in compositions containing
sufficient amine to result in loss of activity of a tin-containing
catalyst for the formation of polyurethanes. Preferably, at least about
0.1, more preferably about 0.05 to about 4, most preferably about 0.2 to
about 1 part of amine is used per part of alkylene glycol chain extender
because these amounts of amine aid in achieving compatibility of glycols
in active hydrogen compounds using amounts of urea insufficient to result
in gels in the active hydrogen composition. Most preferably, the
composition contains about 0.5 to about 20, even more preferably from
about 1 to about 20 parts of the amine per 100 parts of relatively high
equivalent weight active hydrogen compound because these amounts of amine
are effective in preparing solutions of transition metal carboxylates. It
is within the skill in the art to ascertain relative proportions of
relatively high equivalent weight compound, alkylene glycol if desired,
urea compound, transition metal carboxylate, and, optionally, amine useful
in a specific application using the teachings herein. Amounts required for
compatibilization, when needed, and catalysis are functions of
characteristics of the composition such as the identity and amounts of
components in the composition. For instance, when an amine present in the
composition acts as a compatibilizer, the amount of urea compound needed
for compatibilization is advantageously reduced. When another component,
for instance, an amine has catalytic activity, relatively less urea
compound and transition metal carboxylate may be needed to ensure adequate
catalysis and also to provide desirable other benefits of the present
invention, such as mold release and reduced staining of vinyl-based
polymeric cladding.
As is well known in the art, a polyurethane formulation typical includes
one or more polyisocyanates and one or more isocyanate-reactive, e.g.,
active hydrogen containing, compounds. Any suitable organic compound
containing at least two active hydrogen containing groups as determined by
the Zerewitinoff method may be used as an active hydrogen compound. Active
hydrogen compounds are compounds having hydrogen containing functional
groups which will react with an isocyanate group. The Zerewitinoff test
described by Kohler in the Journal of the American Chemical Society, Vol.
49, page 3181 (1927) predicts the tendency of a hydrogen-containing group
to react with isocyanates. Suitable active hydrogen compounds are those
conventionally employed in the preparation of polyurethanes such as the
compounds described in U.S. Pat. No. 4,394,491, particularly in columns 3
through 5 thereof, wherein the compounds are called polyahls, which patent
is incorporated herein by reference in its entirety.
The equivalent weight of the active hydrogen compound is not critical,
although as noted hereinabove it has been shown in parent application U.S.
patent application Ser. No. 398,802, filed Aug. 25, 1989, now allowed,
that the use of the transition metal carboxylate and urea together is also
effective for compatibilizing relatively high equivalent weight active
hydrogen compounds and relatively low equivalent weight active hydrogen
compounds which are present in normally incompatible proportions. The term
"relatively high equivalent weight" is used to refer to an equivalent
weight (molecular weight per active hydrogen-containing group e.g. --OH,
--NH.sub.2, --SH) of at least about 500, preferably from about 500 to
about 5000. The equivalent weight is preferably from about 700 to about
3000, and more preferably from about 1000 to about 2000. The relatively
high equivalent weight active hydrogen compound also advantageously
contains an average of at least about 1.8, preferably from about 1.8 to
about 6, more preferably about 4 to about 6, nominal active hydrogen
containing groups per molecule. The active hydrogen groups are preferably
hydroxyl groups, amine groups or mixtures thereof: more preferably
hydroxyl groups.
Relatively high equivalent weight active hydrogen components most commonly
used in polyurethane production are those compounds having at least two
hydroxyl groups, which compounds are referred to as polyols.
Representatives of the suitable polyols are generally known and are
described in such publications as High Polymers, Vol. XVI, "Polyurethanes,
Chemistry and Technology" by Saunders and Frisch, Interscience Publishers,
New York, Vol. I, pp. 32-42, 44-54 (1962) and Vol. II, pp 5-6 and 198-199
(1964); Kunststoff-Handbuch, Vol. VII, Vieweg-Hochtlen,
Carl-Hanser-Verlag, Munich, pp. 45-71 (1966); and Organic Polymer
Chemistry by K. J. Saunders, Chapman and Hall, London, pp. 323-325 (1973)
and Developments in Polyurethanes, Vol. 1, J. M. Buist, ed., Applied
Science Publishers pp. 1-76 (1978).
Typical polyols include polyester polyols, polyester amide polyols, and
polyether polyols having at least two hydroxyl groups. Polyethers and
polyesters having hydroxyl terminated chains are preferred for use as
relatively high equivalent weight active hydrogen containing compounds for
use in polyurethanes suitable for use in the practice of the invention.
Examples of polyols also include hydroxy functional acrylic polymers,
hydroxyl-containing epoxy resins, polyhydroxy terminated polyurethane
polymers, polyhydroxyl-containing phosphorus compounds and alkylene oxide
adducts of polyhydric thioethers, including polythioethers, acetals,
including polyacetals.
Polyether polyols are preferably employed in the practice of this invention
because they are resistant to hydrolysis. Preferred among polyether
polyols are polyalkylene polyether polyols including the polymerization
products of oxiranes or other cyclic ethers such as tetramethylene oxide
in the presence of such catalysts as boron trifluoride, potassium
hydroxide, triethylamine, tributyl amine and the like, or initiated by
water, polyhydric alcohols having from about two to about eight hydroxyl
groups, amines and the like. Illustrative alcohols suitable for initiating
formation of a polyalkylene polyether include ethylene glycol,
1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol,
1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentane diol, 1,7-heptane
diol, glycerol, 1,1,1-trimethylolpropane, 1,1,1-trimethylolethane,
hexane-1,2,6-triol, alpha-methyl glucoside, pentaerythritol, erythritol,
pentatols and hexatols. Sugars such as glucose, sucrose, fructose, maltose
and the like as well as compounds derived from phenols such as
(4,4'-hydroxyphenyl)2,2-propane, and the like are also suitable polyhydric
alcohols for forming polyether polyols useful in the practice of the
invention.
The polyether is more preferably a polymer of one or more C.sub.2 -C.sub.8
cyclic ethers such as ethylene oxide, propylene oxide, butylene oxide,
styrene oxide, tetrahydrofuran, and the like. Di- and/or trifunctional
polymers of ethylene oxide and/or propylene oxide are preferred. The
preferred polyethers are suitably block or random copolymers of propylene
and ethylene oxide: but are more preferably block copolymers, most
preferably block copolymers having ethylene oxide blocks at the termini of
the polyethers such that there are primary hydroxyl groups on the
polyethers. Such block copolymers are referred to as ethylene oxide capped
polyols. The ethylene oxide caps preferably comprise at least about 10
weight percent of the polyol to produce high reactivity desirable for RIM
processes.
Polyamines are also suitable for use in relatively high equivalent weight
active hydrogen components in polyurethanes and include polyether
polyamines: polyester polyamines: amine-functional polymers such as amine
functional acrylates. amine terminated acetal resins, amine terminated
urethanes, amine containing polyesters, and the like. Suitable amines
include those having terminal primary or secondary aliphatic or aromatic
amine groups, including those having terminal aromatic amine functionality
such as p-amino phenoxy groups, p-amino m-methyl-N-phenyl carbamate groups
and the like. Compositions of amines with polyols are also suitably used
as active hydrogen components. When amines are used as at least a portion
of the active hydrogen component, polyurea and polyureaurethane linkages
are formed. Useful amines include polyoxyalkylene polyamines and
cyanoalkylated polyoxyalkylene polyamines having equivalent weights
preferably from about 500 to about 10,000 and, more preferably, from about
500 to about 5000.
Among amines, amine-terminated polyethers are preferred for use in the
practice of the invention. Amine-terminated polyethers are prepared from
the polyether polyols described above by amination thereof. Amination is
described in, for example, U.S. Pat. Nos. 3,161,682; 3,231,619; 3,236,895:
3,436,359: and 3,654,370, which are incorporated herein by reference. For
amination, it is generally desirable that the terminal hydroxyl groups in
the polyol be essentially all secondary hydroxyl groups for ease of
amination. Secondary hydroxyl groups are introduced into a polyol produced
from ethylene oxide by capping the polyol with higher alkylene oxides,
that is, with alkylene oxides having more than two carbon atoms.
Alternatively, secondary hydroxyl groups result from producing a polyol
from higher alkylene oxides.
Generally, amination does not result in replacement of all the hydroxyl
groups by amine groups. An aminated polyether polyol is selected to have a
percentage of amine groups relative to hydroxy groups of from 0 to 100,
preferably from about 5 to about 95 percent, depending on the physical
properties desired in a resulting polyurethane. The amine groups are
generally primary, but secondary amine groups may be formed. Beneficially,
the amine-terminated polyols have an average functionality of from about 2
to about 6 amine groups per molecule. In the case of amines, the term
"functionality" is used herein to refer to the number of amine groups,
which may be primary or secondary, in the molecule. Advantageously, the
amine-terminated polyols have an average equivalent weight of at least
about 500, preferably an average weight per active hydrogen-containing
group from about 500 to about 5000, more preferably from about 500 to
about 2500. The process of utilizing aminated polyols disclosed in U.S.
Pat. Nos. 4,530,941 and 4,444,910 illustrate processes for using such
compounds. Those patents are incorporated herein by reference.
The formulations of the present invention may also include, as a chain
extender, an alkylene glycol, preferably an .alpha.,.delta.-alkylene
glycol, which can be compatibilized in the compositions of the present
invention, when used with a relatively high equivalent weight active
hydrogen compound in incompatible proportions.: Suitable alkylene glycols
include those having from about 2 to about 8, preferably about 2 to about
6, more preferably about 2 to about 4 carbon atoms. Exemplary chain
extenders include ethylene glycol, 1,4-butanediol, 1,6-hexamethylene
glycol, 1,8-octanediol and the like. Ethylene glycol and 1,4-butanediol
are most preferred.
Although the compositions of the present invention may contain an amount of
glycol chain extender at which the chain extender and relatively high
equivalent weight active hydrogen compound are normally incompatible in
the absence of a stabilizer, the composition preferably contains about 5
to about 60, more preferably about 10 to about 40 parts by weight of chain
extender per 100 parts by weight relatively high equivalent weight active
hydrogen compound because vitrification is often observed when there is
present more than about 40 parts of glycol. It has been found that
polyurethanes having particularly desirable properties may be prepared
from blends containing an amount of chain extender within the preferred
and more preferred ranges.
The active hydrogen component, admixed if desired with other components as
described hereinabove, is reacted with at least one polyisocyanate
component to form a polyurethane. Both aliphatic and aromatic
diisocyanates are useful for this purpose. Suitable aromatic diisocyanates
include, for example, m-phenylene diisocyanate, p-phenylene diisocyanate,
2,4- and/or 2,6-toluene diisocyanate (TDI), naphthylene-1,5-diisocyanate,
1-methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylenediisocyanate,
3,3'-dimethoxy-4,4'-biphenyldiisocyanate, 2,4'- and/or
4,4'-diphenylmethanediisocyanate (MDI) and derivatives thereof including
polymeric derivatives. Preferred among the aromatic polyisocyanates are
the isomers and derivatives of TDI and MDI.
Exemplary aliphatic polyisocyanates include isophorone diisocyanate,
cyclohexane diisocyanate, hydrogenated diphenylmethanediisocyanate
(H.sub.12 MDI), 1,6-hexamethylenediisocyante and the like. Of these,
hexamethylenediisocyanate and H.sub.12 MDI are most preferred.
Biuret, urethane, urea, uretonimine and/or carbodiimide containing
derivatives, including prepolymers, of the foregoing polyisocyanates are
also suitable.
In preparing the polyurethane, the polyisocyanate is employed in an amount
to provide about 0.9 to about 1.5, preferably about 1.0 to about 1.25,
more preferably about 1.0 to about 1.05, isocyanate groups per active
hydrogen-containing group present in the reaction mixture. These ratios of
isocyanate groups to active hydrogen-containing group are referred to
herein as isocyanate index.
The formulations of the present invention can be prepared by any admixing
of active hydrogen, i.e., isocyanate reactive, compound, urea compound,
transition metal carboxylate, and glycol chain extender if desired, that
results in a homogeneous composition. Preferably. a first admixture of the
urea and a glycol chain extender is formed, advantageously by shaking or
stirring the materials together, preferably at about ambient temperature
for convenience. When an amine is used, a second admixture of the
transition metal carboxylate and the amine is formed, advantageously by
mixing them at a temperature of at least about 50.degree. C. until there
is no visible evidence of two phases. preferably for at least about 30
minutes. The two admixtures are then combined with the relatively high
equivalent weight compound and stirred using mild heat, e.g., about
35.degree. C., as necessary to achieve a single phase. Alternatively, the
urea compound or the carboxylate can be solubilized in the isocyanate
compound.
In addition to the foregoing critical components, other additives which are
useful in preparing polyurethanes may be present in the stabilized
composition. Among these additives are catalysts, blowing agents,
surfactants, crosslinkers, antioxidants, UV absorbers, preservatives,
colorants, particulate fillers, reinforcing fibers, antistatic agents,
internal mold release agents and the like.
Suitable blowing agents, which are optionally employed herein, include
water, halogenated methanes such as methylene chloride,
dichlorodifluoromethane, trifluoromonochloromethane and the like, the
so-called "azo" blowing agents, finely divided solids and the like.
Preferably, water is selected as at least one blowing agent, and more
preferably water is used as the sole blowing agent. However, in preparing
noncellular or microcellular polyurethanes the use of these blowing agents
is not preferred. In making microcellular polyurethanes, having a density
from about 600 to about 1500 Kg/m.sup.3, it is preferred to reduce density
by dissolving or dispersing a gas such as dry air or nitrogen into the
composition prior to its reaction with a polyisocyanate. Production of
semi-flexible polyurethanes, such as for automotive interior trim and the
like, is particularly preferred, and more preferred is production of such
using water, preferably alone or, in another embodiment, in combination
with other blowing agents.
Suitable surfactants include silicone surfactants and fatty acid salts,
with the silicone surfactants being preferred. Such surfactants are
advantageously employed in an amount from about 0.01 to about 2 parts per
100 parts by weight relatively high equivalent weight active hydrogen
compound.
Suitable fillers and colorants include calcium carbonate, alumina
trihydrate, carbon black, titanium dioxide, iron oxide, flaked or milled
glass, mica, talc and the like. Suitable fibers include glass fibers,
polyester fibers, graphite fibers, metallic fibers and the like.
While additional catalysts for forming polyurethanes are, optionally,
present in addition to the amine, urea and transition metal carboxylate in
the compositions of the invention, additional catalysts are advantageously
not necessary and, preferably, are not used. When additional catalysts are
used, they are preferably catalysts which do not exhibit a substantial
loss of activity when stored with other components of the compositions for
times suitable for particular applications. More preferably, the catalysts
lose less than about 50, most preferably less than about 25 percent of
their reactivity (as measured by gel time) when stored with other
components of a composition of the invention for a period of at least
about 6 months at a temperature of at least about room temperature (e.g.
25.degree. C.). More preferably, tetravalent organometallic tin-containing
catalysts which lose activity in the presence of amines, such as dialkyl
tin dicarboxylates, tetraalkyl tins and tin oxides, particularly stannous
oxide, are present in amounts insufficient to substantially increase the
rate of polyurethane formation, (as measured by gel time). An increase of
less than about 10 percent in gel time is considered insubstantial. Most
preferably there is less than about 0.001 weight percent tetravalent tin
catalyst. Specific catalysts are within the skill in the art and include
those catalysts described, for instance, in U.S. Pat. No. 4,269,945,
particularly column 4, line 46 through column 5, line 25, which is
incorporated herein by reference.
The reaction of the components used in the present invention is preferably
carried out by forming a mixture therewith and introducing the mixture
into a suitable mold for curing. Conventional casting techniques may be
used, wherein the components are mixed and poured into the mold, where
they cure upon heating. However, especially when more reactive components
are used, it is preferred to conduct the reaction using a reaction
injection molding (RIM) process. In such process, the components are
subjected to high shear impingement mixing and immediately injected into a
closed mold where curing takes place. In either the conventional casting
or RIM techniques, in-mold curing takes place at least to an extent that
the part retains its shape during demolding and subsequent handling.
However, complete curing, i.e., curing to a point at which no additional
discernable reaction occurs, may take place either in the mold or in a
post-curing step which is conducted after demolding. If needed, postcuring
of the polyurethane is advantageously conducted at a temperature of from
about 250.degree. F. to about 350.degree. F. for a period of from about 1
minute to about 24 hours, preferably about 1 minute to about 3 hours.
While the invention is useful in forming any polyurethane, particularly a
molded polyurethane, it is particularly useful in the preparation of
elastomeric polyurethanes using automated RIM processes. The invention is
particularly important in producing high modulus RIM polyurethanes,
preferably those having a flexural modulus greater than about 2,000 psi,
more preferably greater than about 5,000 psi, most preferably greater than
about 10,000 psi, and even more preferably greater than 20,000 psi as
measured by the procedure of ASTM D-747-86. Polyurethanes of the invention
are often used to prepare automobile parts such as fascia, molded window
gaskets, bumpers, stearing wheels, vehicle armrests, dashboards and other
interior trim and the like, as well as for non-automotive uses such as
beer barrel skirts, shoe soles and the like.
When polyurethanes prepared from the compositions of the invention are
molded, particularly in a RIM process, they advantageously exhibit self
release properties, that is, they release from a mold more easily than do
polyurethanes containing the same other components, but not containing the
combinations of urea and transition metal carboxylate of the invention.
Particularly unexpectedly, semi-flexible polyurethanes, which are
generally microcellular, exhibit self release properties and, when
applicable, experience compatibilization of glycols. Such release
properties are observed even when the polyurethane has been blown in part
or, especially, solely with water.
In a particularly preferred embodiment of the present invention, the
polyurethane is molded using a vinyl-based polymer as a substrate. For
example, a polyvinyl chloride sheet may be placed into the mold at a
desired location such that the polyurethane cures, with or without the
formation of cells to reduce density, against and adhered to the sheet. In
the present invention, the combination of the transition metal carboxylate
and the amine along with the urea results in both improvement of the
adhesion as well as the reduction of the tendency of the vinyl-based
polymer to discolor with time. Particularly preferred for use herein is a
polyvinyl chloride cladding.
The following examples are provided to illustrate the invention but are not
intended to limit the scope thereof. All parts and percentages are by
weight unless otherwise indicated.
EXAMPLE 1
A formulation for preparing a semi-flexible polyurethane, consisting of the
components and amounts shown in Table 1, is prepared using conventional
polyurethane mixing and formulation techniques.
TABLE 1
______________________________________
Amount
(parts based on
Component 100 parts of polyol)
______________________________________
Polyether Polyol.sup.1
60
Copolymer Polyol.sup.2
40
Cell opener.sup.3 4
Triethanolamine 85%
1.5
Water 2.2
Amine-containing Compound.sup.4
2
Zinc Laurate 2
Urea 1
Surfactant.sup.5 0.65
______________________________________
.sup.1 A 5,000 molecular weight, glycerininitiated, ethyleneoxide capped
polyether polyol.
.sup.2 A styreneacrylonitrile dispersion (25 percent solids) in a 5,000
molecular weight, glycerininitiated, ethylene oxidecapped polyol.
.sup.3 A 12,000 molecular weight polyether polyol.
.sup.4 An ethylene diamine initiated polyether polyol.
.sup.5 TEGOSTAB B4113*, a silicone surfactant available from Goldschmidt
Chemical Corporation.
The components shown in Table I are maintained at room temperature
(60.degree.-75.degree. F.), and then combined with a polymeric MDI
(average functionality about 2.3), in a ratio of 0.4 parts of the
isocyanate to 1 part of the polyol formulation. The isocyanate is added to
the formulation and mixed at 2,500 rpm for approximately 6 seconds. The
resulting mixture is poured into a mold cavity measuring 6 inches by 6
inches by one-half inch. The mold is maintained at 125.degree. F. As soon
as the pour is completed the mold is closed. The mold, which has
previously been treated with an external mold release known as DELIFT*
release AID-14, available from Kramer Chemical Corporation, is then opened
and the completed part is removed. The time in the mold is 4 minutes. The
result is a semi-flexible, all-water blown part.
The experiment is repeated 10 times but without further application of the
external mold release after the molding of the first part. Each of the
parts releases without significant or unacceptable difficulty or
deformation.
EXAMPLE 2
Comparative
The experiment of Example 1 is substantially repeated except that a
different formulation is used, as described in Table 2.
TABLE 2
______________________________________
Amount
(parts based on
Component 100 parts of polyol)
______________________________________
Polyether Polyol.sup.1
60
Copolymer Polyol.sup.2
40
Triethanolamine 85%
1.5
Water 2.3
Amine-containing Compound.sup.3
0.5
Zinc Laurate 0.5
Urea 1
Surfactant.sup.4 0.25
______________________________________
.sup.1 A 5,000 molecular weight, ethyleneoxide capped polyether polyol.
.sup.2 A styreneacrylonitrile-containing copolymer polyol having a solids
content of about 25 percent.
.sup.3 An ethylene diamine initiated polyether polyol.
.sup.4 TEGOSTAB B4113*, a silicone surfactant available from Goldschmidt
Chemical Corporation.
The polyurethane is foamed in the mold as described in Example 1, except
that a sheet of polyvinyl chloride is applied against one surface of the
mold as a substrate for the polyurethane foam. An identical formulation,
but lacking the urea and zinc laurate, is also prepared and foamed against
an identical polyvinyl chloride substrate. A staining study is then
carried out under which a sample of the urea/zinc laurate/vinyl
composition and the vinyl composition lacking the urea and zinc laurate
(i.e., the "conventional foam") are together subjected to 121.degree. C.
temperature for 500 hours (21 days). At the end of this time the samples
are removed from the heating oven and visually examined for staining and
for brittleness.
The vinyl adhered to the conventional foam shows small darker spots and is
significantly more brittle. The vinyl adhered to the foam containing urea
and zinc laurate exhibits no visual staining. A MINOLTA* CR200 Chromameter
is used to determine the color change, called the Delta E value, of the
polyvinyl chloride in the samples. The urea/zinc laurate polyvinyl
chloride surface distal to the polyurethane foam shows a Delta E value of
1.9, while polyvinyl chloride without any adhered foam, but which has been
subjected to the same heating process, shows a Delta E of 1.72. In
contrast, the vinyl adhered to the conventional foam has a Delta E value
of 7.35.
EXAMPLES 3-9
Comparative
An admixture of 10 parts by weight ethylene glycol and 2 parts of the urea
compound indicated in Table 1 is formed by stirring at room temperature.
After about 30 minutes, 100 parts by weight of a 5000 molecular weight,
glycerine initiated poly(propylene oxide) which is ethylene oxide capped
(hereinafter Polyol A) is added to the admixture and stirred for 15
minutes to form a first admixture. A second admixture of 2 parts by weight
of zinc laurate with 7 parts by weight of difunctional, amine terminated
poly(propylene oxide) having an average molecular weight of about 400,
commercially available from Texaco Chemical Corp. under the trade
designation Jeffamine.RTM.D400 (hereinafter Amine A) is formed by stirring
at about 65.degree. C. for 30 minutes.
For each of Examples 3-9, 112 parts by weight of the first admixture is
mixed with 9 parts by weight of the second admixture by stirring for 10
minutes at a temperature of about 20.degree. C. to form a "B-Side"
mixture. A sample of each "B-Side" mixture is thoroughly mixed within a
sufficient sample of carbodiimide-modified diphenylmethanediisocyanate
having an average equivalent weight of about 143 to produce a mixture
having an isocyanate index of about 1.03.
The resulting mixture is quickly poured into a cup at room temperature, and
the time from mixing the isocyanate and the "B-Side" mixture until a gel
too stiff to stir manually is formed is recorded in Table 3 as the gel
time.
For Comparative Samples A-G, the procedure of Examples 3-9 is followed
omitting the zinc laurate and Jeffamine.RTM.D400. Gel times for the
comparative are also recorded in Table 3.
A gel time of about 40 seconds or less is interpreted as indicating that
the corresponding formulation is sufficiently reactive to be commercially
useful in a high pressure automatic RIM process.
TABLE 3
______________________________________
Comparative
Comparative
Samples Examples
Candidate
Samples (gel time in
Example
(gel time
Urea No.* sec.) No. in sec.)
______________________________________
Phenyl A* 100+(no 1 Immediate
urea reaction) reaction;
semisolid
at 59 sec.
1,1- B* 100+(reacts
2 Soft solid
dimethyl slowly to a at 21 sec.
urea solid
polymer)
1-methyl
C* 100+ 3 26
urea
1,3- D* 100+ 4 37
dimethyl
urea
1,1,3,3-
E* 100+ 5 72
tetramethyl
urea
1,1-diethyl
F* 100+ 6 26
urea
Tri- G* 100+ 7 40
methylene
Urea
______________________________________
*indicates not an example of the present invention.
The data in Table 3 shows that, except when the urea is tetrasubstituted,
formulations having polyol, glycol, urea compound, amine and zinc laurate
in the "B-side" mixture exhibit sufficient reactivity to be useful in
automated RIM processes, whereas certain formulations not having the amine
and zinc laurate do not exhibit sufficient reactivity.
The data in Table 3 show that polymers having good physical properties can
be formed using compositions of the invention with or without additional
catalyst. The compositions are sufficiently reactive without additional
(tin-containing) catalyst to give demolding times of 30 seconds. For
comparison, it is noted that similar demolding times cannot be achieved
using similar compositions that lack conventional polyurethane formation
catalysts from which either the urea or the zinc laurate is omitted. When
tin catalyst is used with the zinc laurate and urea, the reaction is so
fast that it may be impracticable for use in some commercial RIM
processes.
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